Unihedron SQM-LU, SQM-LU-DL-V Operator's Manual
SQM-LU Operator’s Manual
c
Copyright 2005 - 2017
Version: 20170728
Company information
Mailing address Unihedron
4 Lawrence Avenue
Grimsby, Ontario L3M 2L9
Canada
Telephone (905) 945-1197
Fax (905) 945-6770
Website unihedron.com
Contents
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1 QuickStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1.1 Other software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1.2 FITS integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1 Getting accurate readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1 Seeing conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2 Light pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.3 Other luminance scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3 Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Light measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Communication to the PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 Hardware connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6 Software development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1 Writing your own software interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.2 Pascal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7 Unihedron Device Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1 Getting UDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2.1 System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2.2 Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2.3 Mac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2.4 Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3.1 Start up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3.2 Main screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3.3 Main menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.4 File menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.5 Tools menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.3.6 Help menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.4 Information tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.5 Log Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.6 Calibration tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.7 Report Interval tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3
Contents
7.8 Firmware tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.9 Configuration tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.9.1 Sensor arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.10 Simulation tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.10.1 Simulation from file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.11 Accessory options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.11.1 Humidity accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.11.2 Display accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.11.3 LED accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.11.4 Relay accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.12 Command line parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8 Commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.1 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.2 Response details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.1 Reading request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.2 Unaveraged reading request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.3 Unit information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.3 Calibration commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.3.1 Calibration information request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.3.2 Light calibration command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.3.3 Dark calibration command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.3.4 Disarm calibration command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.3.5 Manually set light calibration offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.3.6 Manually set light calibration temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.3.7 Manually set dark calibration time period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.3.8 Manually set dark calibration temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.4 Accessories commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.4.1 Humidity / Temperture sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.4.2 Display accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.4.3 LED accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.4.4 Relay accessory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
8.5 Continuous reporting commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.6 Setting Interval reporting parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.6.1 Interval reporting period setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.6.2 Threshold setting for interval reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.6.3 Interval setting response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
8.7 Simulation commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1 Mechanical installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1.1 Cover selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1.2 Cover calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.1.3 Cover maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10 Default settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
11 Firmware upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
11.1 Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
12 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
12.1 Recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
12.2 Light calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
12.3 Dark calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
12.4 Confirmation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4 Unihedron SQM-LU Operator’s Manual - 20170728
13 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
14 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
15 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
List of Figures
2.1 Mpsas interpretive scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 Mpsas vs NELM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1 Front of unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Back of unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1 Wired connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1 Splash screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2 File menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3 File Open dialog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.4 View menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.5 View : Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.6 View:Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.7 Data logging header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.8 Set Location dialog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.9 Tool : old log to dat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.10 Tool : dat to Moon csv . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.11 Tool : Comm terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.12 Help menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.13 Help : About . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.14 Found device (single) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.15 Found device (multiple) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.16 USB connection details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.17 Ethernet connection details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.18 RS232 connection details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.19 Information tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.20 Log Continuously screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7.21 Log Continuously Trigger tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7.22 Log Continuously Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.23 Log Continuously Annotation tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.24 Log Continuously GPS tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.25 Calibration tab (initial) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.26 Calibration tab (populated) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.27 Report interval tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.28 Firmware tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.29 Firmware selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.30 Configuration tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.31 Light calibration confirmation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.32 Dark calibration confirmation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5
7.33 Sensor arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.34 Fig:Simulation tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.35 Accessories tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
9.1 Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
9.2 Example cover calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
List of Tables
2.1 Apparent Magnitudes of Known Celestial Objects adapted from [2] . . . . . . . . . . . . . . . . . . . . . . 10
7.2 simin.csv field description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.3 Log continuous command line parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.4 Select device command line parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.5 Select device command line parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.1 Summary of standard commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.2 Reading request response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.3 Unaveraged reading request response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.4 Unit information request response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.5 Calibration information request response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.6 Light calibration response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.7 Dark calibration response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.8 Disarm calibration response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.9 Response for manual setting of light calibration offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.10 Response for manually setting of light calibration temperature . . . . . . . . . . . . . . . . . . . . . . . . 45
8.11 Response of manually setting dark calibration time period . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.12 Response for manually setting of dark calibration temperature . . . . . . . . . . . . . . . . . . . . . . . . 46
8.13 Humidity/temperature command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.14 Humidity/temperature response summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.15 Display accessory command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.16 Display accessory response summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.17 LED accessory command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.18 LED accessory response summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.19 Relay accessory command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
8.20 Relay accessory response summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
8.21 Summary of standard commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.22 Continuous reporting command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.23 Response of all continuous reporting requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
8.24 Interval report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.25 Response of viewing or setting interval reporting parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 54
8.26 Response of request for internal simulation values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
8.27 Request simulation (S....x) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
8.28 Response of setting simulation values (S...x) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
13.1 Reading seem too bright . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
13.2 Reading is 0.00mpsas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6
13.3 Cannot Find UDM software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
13.4 Driver not found . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
13.5 USB device not found, or more than one device on the same COM port . . . . . . . . . . . . . . . . . . . 62
13.6 Recording stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
13.7 Meter cannot be found by PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
13.8 Meter cannot be found by Windows operating system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
13.9 Cannot get a reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
14.1 Glossary of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
List of Equations
2.1 MPSAS to cd/m2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 NELM to MPSAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 MPSAS to NELM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1 Raw Temperature to degC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
8.2 degC to Raw Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
7
1 Introduction
Thank you for purchasing the SQM-LU. You will soon be on your way to collecting scientific data.
The SQM series of products have been used in the following applications:
• Quantitatively comparing the sky brightness at different astronomical observing sites.
• Documenting the evolution of light pollution.
• Setting planetarium dome illumination to mimic the skies that people are likely to experience elsewhere in the city.
• Monitoring sky brightness through the night, night-to-night, and year-to-year for astronomical observation records.
• Determining which nights show the greatest promise for finding the ’faintest fuzzies’.
• Calibrating the effect of sky brightness on qualitative measures such as the Bortle Scale or NELM.
• Investigating how sky brightness correlates with the solar cycle and month-to-month sunspot activity.
• Helping to provide local ground truth for future sky brightness prediction with the Clear Sky Clock.
• Helping CCD users make a correlation between the SQM reading and when the background reaches some ADC
level.
• Assisting Sea Turtle researchers in studying the amounts of light in areas where turtle hatchlings are affected by
artificial lights.
• Researching bird-song synchronization with dawn.
• Researching twilight brightness changes with the addition of external Neutral Density filters. Unihedron offers
adapters to attach such filters onto the meter.
1.1 QuickStart
1. Connect the SQM-LU meter to the computer with the supplied USB cable. Wait for any device drivers to automatically load (if required). You may have to visit www.FTDIchip.com to get the latest VCP drivers if they do not get
installed automatically.
2. Ensure that your computer date and time is up-to-date.
3. Install and launch UDM (Unihedron Device Manager software supplied on the CD from your File Manager).
4. Click the “Find” button to find attached devices, then click on the SQM-LU that you connected.
5. Click on “Reading” to get a reading from the SQM-LU.
6. Logging and plotting can be done from the “Log Continuous” button.
1.1.1 Other software
• If you are using Windows, you may want to use Knightware SQM-Reader from www.knightware.biz/sqm .
• The CD contains examples of software (Perl, Python, etc.) for various functions that connect to the meter.
1.1.2 FITS integration
Some programs (listed below) gather information from the Unihedron Sky Quality meter products and insert that data
into the Flexible Image Transport System (FITS) header.
• MaxPilote (Freeware) incorporates SQM readings from an SQM-LE/SQM-LU into the FITS header while at the
same time provide constant readings in a live and updated Data Window.
8
• CCDAutoPilot
• FITS4Win2 uses the MPSAS keyword for sorting and filtering image files.
1.1 QuickStart
Unihedron SQM-LU Operator’s Manual - 20170728 9
2 Measurements
The SQM-LU provides readings in Magnitudes per square arcsecond, abbreviated as: mpsas, and written mathematically
mag
as
Mpsas is a logarithmic measurement which means that large changes in sky brightness correspond to relatively small
numerical changes. A difference of 5 magnitudes is a factor of 100 times the intensity. Therefore a sky brightness 5.0
darker corresponds to a reduction in photon arrival rate of a factor of 100.
The following schematic gives a rough idea of how to interpret the readings of the SQM:
Magnitudes are an astronomical unit of measure for object brightness. Brighter objects have a lower magnitude and
darker objects have a higher magnitude value. For example; a star that is 6th magnitude is brighter than a star that is
11th magnitude.
The star Vega is used a the reference point of ≈ 0 magnitude. Table 2.1 shows the apparent magnitude of some common
known celestial objects.
arcsec
.
2
mag
arcsec
Figure 2.1: Mpsas interpretive scale
2
Table 2.1: Apparent Magnitudes of Known Celestial Objects adapted from [2]
App. Mag. Celestial Object
−26.73 Sun
−12.6 full Moon
−4.7 Maximum brightness of Venus
+0.03 Vega, the original zero point
+6 Faintest stars observable with naked eye
+27
+30
Faintest objects observable in visible light with 8m ground-based telescopes
Faintest objects observable in visible light with Hubble Space Telescope
Arcsecond is the definition of an arc being divided up into seconds as follows.
1. There are 360 degrees in a circle.
2. There are 60 arcminutes in a degree, and 21600 arcminutes in a circle.
10
3. There are 60 arcseconds in an arcminute, and 1296000 arcseconds in a circle.
Square arcsecond (arcsec2) is the area covered by a square measuring 1arcsec × 1arcsec .
2.1 Getting accurate readings
Magnitude per square arcsecond is the definition of brightness in magnitudes spread out over one square arcsecond
of the sky. For example; if the SQM provides a reading of 20.00 mpsas, that would be like saying that a light of a 20
magnitude star brightness was spread over one square arcsecond of the sky.
The ”magnitudes per square arcsecond” numbers are commonly used in astronomy to measure sky brightness. More
details can be found at www.stjarnhimlen.se/comp/radfaq.html
Each magnitude lower (numerically) means just over 2.5 times as much more light is coming from a given patch of sky.
A change of 5 mags/sq arcsec means the sky is 100x brighter.
Also, a reading of greater than 22.0 is unlikely to be recorded and the darkest we’ve personally experienced with the
SQM is 21.80.
th
2.1 Getting accurate readings
Various factors will cause the night sky brightness to fluctuate. Taking more readings will be useful in ruling out spurious
events. The SQM gathers light for at least a one second period, and the brightness report is based on the light that was
accumulated during that time.
At the darkest sites, natural variations in conditions such as airglow and the brightness of the zodiacal light are limiting
factors.
Prevent artificially high (dark) readings by ensuring that there is nothing blocking the view of the sensor. Avoid taking
readings near trees or buildings that may block the sensor.
Prevent artificially low (bright) readings by ensuring that there are no lighted objects (street lamps, the moon, etc.)
that shine into the sensor at any angle.
2.1.1 Seeing conditions
The apparent blurring/transparency and twinkling (scintillation) of stars is due to wind in the upper atmosphere that
causes water molecules to distort the light from space.
Stars are too small in comparison to the entire SQM field of view, so scintillation is not expected to alter the SQM
reading significantly.
2.1.2 Light pollution
Undesirable artificial light that reaches you is considered to be light pollution. Much of this light comes from outdoor
illumination of parking lots, street lamps, office buildings, advertising signs, etc..
Other causes of extra light in the night sky are listed below:
Aurora
Charged particles emitted from the Sun are directed to the poles of the earth by the Earth’s magnetic field. These particles
collide with atoms in the atmosphere and cause light to be emitted. Aiming the meter at the polar regions during Aurora
Borealis (in the North) or Aurora Australis (in the South) will reduce the reading (lighter). Aiming the meter towards
the equator will increase the reading (darker) under these conditions.
Airglow
Airglow is light produced by various phenomenon in the atmosphere which prevent the sky from being totally dark. Effects
of the magnetic poles of the Earth may cause airglow to be brighter near the poles.
Unihedron SQM-LU Operator’s Manual - 20170728 11
2 Measurements
The Milky Way
As one goes to sites with darker surface brightnesses, the fraction of the total light received by the SQM-LU which can
be attributed to the Milky Way bulge increases and so the “offset” in mpas will be larger (due to the Milky Way.)
The northern view of the Milky Way contributes about 0.10 mpsas under 21.5 mpsas (moonless) skies.
The southern view of the Milky Way might be as big an effect as 0.56 mpsas in dark skies where it goes near-overhead.
For more information, see Surface Photometries of the Milky Way (Schlosser+ 1997)
vizier.u-strasbg.fr/ftp/cats/VII/199/ReadMe
Moisture
Clouds, fog, and mist will reflect artificial light back down to the Earth causing a brighter (lower) reading. If there is
no artificial light, then clouds may prevent starlight from coming to you and the reading will be darker (higher). This
extra-dark situation can occur in very isolated areas like mountain tops, the ocean, or the desert. You will have to be
aware of this special situation when analyzing readings.
Volcanic eruptions
Dust released into the atmosphere by volcanoes can reflect light from the surface of the earth back down. In a dark
location this dust will prevent the light from stars and Milky Way and produce a darker (higher) reading.
Zodiacal light
The sunlight reflected of off dust particles in the ecliptic plane of our solar system is called zodiacal light.
The amount of light will be different depending on whether the meter is pointed to the poles or plane of the solar
system. It is likely to have less than 2% effect. The primary reason for this small effect is that the brightest and widest
part of the zodiacal light is nearest the horizon where the SQM has almost no sensitivity (due to it being a primarily
zenith-looking device). The portions at higher altitude are the narrowest and faintest and they would barely creep into
the sensitivity cone of the SQM.
2.1.3 Other luminance scales
Candela per square meter (cd/m2) is commonly used by lighting engineers.
To convert the SQM mpsas reading to cd/m2, use Equation (2.1):
[cd/m2] = 10.8 × 104× 10
Naked eye limiting magnitude (NELM)
Quite often astronomers will refer to a sky by the darkest star they can see, for example a “6th magnitude sky”, in that
case you can see 6th magnitude stars and nothing dimmer like 7thmagnitude stars. The term “6thmagnitude skies” is
very subjective to a persons ability to see in the night, for example an older person might say “5thmagnitude skies” but
a young child with better night vision might say “7thmagnitude skies”.
Nobody has performed the task of defining a relationship between the two methods of sky brightness ( x magnitude
skies and magnitudes per square arcsecond) -- probably because one is subjective and the other is objective and a wide
variety of people would have to be polled.
An approximation exists for the conversion between NELM and MPSAS. You can use an NELM converter[5] created
by SQM user K. Fisher to do that conversion, or the chart shown in Figure 2.2 and Equations (2.2) and (2.3).
(−0.4×[mag/arcsec2])
(2.1)
12 Unihedron SQM-LU Operator’s Manual - 20170728
2.1 Getting accurate readings
Figure 2.2: Mpsas vs NELM
Convert NELM (V mags) to MPSAS (B) sky brightness [3]
B
= 21.58 − 5 × log(10
mpsas
(1.586−NELM/5)
− 1) (2.2)
Convert MPSAS (B) sky brightness to NELM (V mags) [4]
NELM = 7.93 − 5 × log(10
(4.316−(Bmpsas/5))
+ 1) (2.3)
NSU
A newly proposed term to define “Natural Sky Units”:
In “natural sky units” (radiance relative to an assumed natural radiance of 21.6 magSQM/arcsec2, see
methods), the range was 0.22 - 2200 NSU. Before the introduction of anthropogenic light, the radiance of a
patch of sky near zenith on moon-free nights is likely to have been nearly always within the range 21 (galactic
center near zenith) to 24 mag/arcsec2 (very thick clouds), or 0.1 - 1.7 NSU.[1]
Unihedron SQM-LU Operator’s Manual - 20170728 13
3 Theory of operation
3.1 Light measurement
The SQM-LU measures the darkness of the night sky to provide readings of magnitudes per square arc second through a
USB connection, and is capable of internally recording readings.
A light sensor (TSL237) provides the micro-controller with a light level, and readings from the temperature sensor are
used to compensate the light sensor readings through the range of operating temperatures.
3.2 Communication to the PC
Commands sent from a PC through the USB cable to the USB interface are relayed to the micro-controller.
The micro-controller responds to commands by sending data strings to the USB interface which are then relayed to the
PC.
Readings are gathered asynchronously by the micro-controller. Requests from the PC are buffered and dealt with as
time permits.
14
4 Specifications
USB connection USB B connector.
5m USB A to USB B cable supplied.
USB FTDI VCP driver, serial port emulator at 115200baud.
Physical Size 3.6” x 2.6” x 1.1”
Meter precision Each SQM-LU is factory-calibrated. The absolute precision of each meter is
believed to be ±10% (±0.10 mag/arcsec2). The difference in zero-point
between each calibrated meter is typically ±10% (±0.10 mag/arcsec2)
Power requirement 18mA (from the 5V USB connection).
Operating temperature range -40◦C to 85◦C
Temperature Accuracy ± 2◦C maximum at 25◦C
Temperature update rate 4.3 seconds, 256 samples taken at 60Hz then averaged.
Figure 4.1: Front of unit
Figure 4.2: Back of unit
15
5 Hardware connections
The SQM-LU requires one connection to a USB hub or a PC for configuring the device and recovering the readings as
shown in Figure 5.1.
Figure 5.1: Wired connection
The maximum length cable per the USB specification is 15ft (3m). USB extenders exist on the market, some work up
to 198ft (60m).
16
6 Software development
The SQM-LU uses the FTDI FT232R chip to communicate as a standard serial port device at 115200 baud using the FTDI
software drivers which are available for all major operating system platforms. Drivers are available from www.ftdichip.com
.
Once the driver is installed, commands can be sent to the SQM-LU using a serial terminal emulator to the serial
communications port that the device routes to.
When connecting the SQM-LU to a PC where the FTDI device driver is loaded, the serial port label will be determined
at connection time.
Each SQM-LU has a unique serial number usually with a prefix of “FT........”. This serial number can be used to
identify the exact SQM-LU device from other USB devices.
6.1 Writing your own software interface
All of the commands and responses of the SQM-LU are documented in Section 8.
To communicate with the SQM-LU, the following general steps are required:
1. A serial 115200 baud connection must be made to the serial port assigned to the SQM-LU.
2. Data commands are sent to the SQM-LU, and it responds with a string of characters.
3. Close the serial port so that other programs can access the SQM-LU. Note: Only one connection can be made to the
SQM-LU at a time. Therefore leaving a connection open constantly prevents other connections from being made.
Various examples of reading from the SQM devices are supplied on the CD and available at the Unihedron website.
Below is an example using Perl to read the SQM USB device:
Listing 6.1: Read SQM-LU using Perl
#!/usr/bin/perl
#Filename: read-sqmlu.pl
#Description: Utility to read Unihedron Sky Quality Meter-LU (USB model)
# Define the required module
use Device::SerialPort;
# Open and configure serial port
$port= Device::SerialPort->new("/dev/ttyUSB2");
$port->user_msg(ON);
$port->baudrate(115200);
$port->parity("none");
$port->stopbits(1);
$port->databits(8);
$port->handshake("none");
$port->write_settings || undef $port;
$port->read_char_time(1); # Wait for each character
# Send request to SQM
$port->write("rx\r");
# Get response from SQM
($count,$saw)=$port->read(255);
# Close the port so that other programs can use the SQM
$port->close;
17
6 Software development
# Print the SQM result to the screen
printf("%s", $saw);
The above program prints a result like this:
r,-09.42m,0000005915Hz,0000000000c,0000000.000s, 027.0C
6.2 Pascal
The UDM program contains many examples of finding the SQM devices and reading data from them. It is open source
and written in Lazarus/FreePascal. The source files for UDM are available here:
unihedron.com/projects/darksky/cd/udm/ .
18 Unihedron SQM-LU Operator’s Manual - 20170728
7 Unihedron Device Manager
The Unihedron Device Manager (UDM) program is intended for use in maintaining and testing the Unihedron connected
Sky Quality Meter products. Windows, Mac, Linux versions of UDM area available on the supplied CD. It is used to:
• Read version information.
• Request readings.
• Read and set calibration data.
• Read and set all other meter parameters.
• Install new firmware.
• Setup and retrieve data from datalogging meters.
• Continuously log data from connected meters.
7.1 Getting UDM
UDM is supplied on the CD that shipped with the SQM-LU. The latest version of UDM is available at the Unihedron
website at this location
www.unihedron.com/projects/darksky/cd/
7.2 Installation
7.2.1 System requirements
The UDM is a fairly simple (but large) program which should run sufficiently on any present-day computer under the
Windows, Mac, or Linux operating systems.
7.2.2 Windows
The Windows version of UDM is in a setup.exe style file located in the Windows subdirectory of the CD, for example:
\Windows\setup1.0.0.38.exe
Simply double-click on that file to start the installation procedure.
7.2.3 Mac
The Mac OSX version of UDM is a dmg file located in the Mac subdirectory of the CD, for example:
/Mac/udm.app.dmg
Drag the app to the /Applications directory.
7.2.4 Linux
The Linux version of UDM is available in a Debian package separately for both 32bit and 64bit systems located in the
Linux directory of the CD, for example:
/Linux/udm 20140821-1 i386.deb
Open the file with package installer program like GDebi.
19
7 Unihedron Device Manager
7.3 Operation
After starting UDM, a list of found devices should appear, if your device is not listed on the screen, try clicking “Find”
once more to search for connected devices.
If more than one SQM device is found, then you will have to select (click) on one of the devices, otherwise if only one
device is found, then click on “Version” or “Reading” of the information tab for more information.
The tabs can be used to select various functions when working with your selected device. These tabs and their functions
are described further in this document.
7.3.1 Start up
After starting the UDM program, a splash screen shown in Figure 7.1 is temporarily shown while the program searches
for attached devices.
Figure 7.1: Splash screen
1. UDM searches for attached USB devices first. This step is fairly quick (a few seconds).
2. UDM then searches for attached Ethernet devices within the reach of the Ethernet network but not outside a firewall.
This step may take about 30 seconds.
If no devices are found, then the main UDM program will be shown with the “found devices box” empty. You can
attach an SQM device to your computer and press the “Find” button to search for the newly connected devices.
If you know that an Ethernet device is connected but it does not show up, then a network problem may be the cause.
Also check the power connection to the SQM-LE.
If you know that a USB device is connected but it does not show up, then there may be a device driver issue. Check
the USB device listing for your operating system. These USB devices should appear as a COMM port. Also, check the
troubleshooting notes in section 13 on page 62 for possible solutions.
7.3.2 Main screen
The main screen of UDM consist of the following sections:
20 Unihedron SQM-LU Operator’s Manual - 20170728
7.3.3 Main menu
7.3 Operation
1. Window controls
2. Menu
3. Found devices box
4. Selected device details
5. Information section
6. Status bar
The main menu of UDM consists of the items; File, View, Tools, Help as defined below.
7.3.4 File menu
The file menu is used for: opening files, finding newly attached devices, and quitting the program as shown in Figure 7.2.
Figure 7.2: File menu
File : Open
The “File : Open” menu item is used to open up previously stored log files or calibration reports.
Unihedron SQM-LU Operator’s Manual - 20170728 21
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